Once I have several markets or stalls, having 1 person for each stall responsible for all goods selling and stocking becomes unmanageable by the game. Like I'll have markets empty yet I have 1000 of each item in stock. Having someone whose specific job either. For each stall or a small building would mean they could leave when a stall is getting low. The small storage is just to help make it smoother. Say the hauler can store 2 items, 10-40 each. (even with tents. Canopies)
The market attendants will check there only if it's unlocked, otherwise they will behave like normal. This is separate building with storage.
For no storage the building should operate like a message board to tell the stall attendants not to fetch goods because the hauler is getting them. For which ever goods they're getting . And it would also let the hauler know if a stall attendant is fetching goods.
I due to the mechanics of the game. I'd rather each stall have an attending and a restalk person. And a small back stock for shorter trips.
Or have haulers as a seperate building all together or attached. To storage yards and granaries.